The Kubernetes Operator Framework Book: Overcome complex Kubernetes cluster management challenges with automation toolkits

✍ Scribed by Michael Dame

• Publisher: Packt Publishing
• Year: 2022
• Tongue: English
• Leaves: 328
• Category: Library

✦ Synopsis

Design and deploy an operator for personal use and public distribution and get to grips with writing, packaging, and distributing a basic operator for a Kubernetes cluster

Key Features

• Develop a holistic understanding of operators and the Operator Framework
• Learn to design and develop your own operators as per industry standards
• Find out how to implement best practices and troubleshoot Kubernetes operators

Book Description

From incomplete collections of knowledge and varying design approaches to technical knowledge barriers, Kubernetes users face various challenges when developing their own operators. Knowing how to write, deploy, and pack operators makes cluster management automation much easier – and that's what this book is here to teach you.

Beginning with operators and Operator Framework fundamentals, the book delves into how the different components of Operator Framework (such as the Operator SDK, Operator Lifecycle Manager, and OperatorHub.io) are used to build operators. You'll learn how to write a basic operator, interact with a Kubernetes cluster in code, and distribute that operator to users. As you advance, you'll be able to develop a sample operator in the Go programming language using Operator SDK tools before running it locally with Operator Lifecycle Manager, and also learn how to package an operator bundle for distribution. The book covers best practices as well as sample applications and case studies based on real-world operators to help you implement the concepts you've learned.

By the end of this Kubernetes book, you'll be able to build and add application-specific operational logic to a Kubernetes cluster, making it easier to automate complex applications and augment the platform.

What you will learn

• Gain insight into the Operator Framework and the benefits of operators
• Implement standard approaches for designing an operator
• Develop an operator in a stepwise manner using the Operator SDK
• Publish operators using distribution options such as OperatorHub.io
• Deploy operators using different Operator Lifecycle Manager options
• Discover how Kubernetes development standards relate to operators
• Apply knowledge learned from the case studies of real-world operators

Who this book is for

This book is for DevOps and cloud engineers, Kubernetes engineers, SREs, developers, and cloud architects interested in automating the management of their Kubernetes clusters. It assumes a basic understanding of core Kubernetes topics or familiarity with Kubernetes and container orchestration.

Table of Contents

1. Introducing the Operator Framework
2. Understanding How Operators Interact with Kubernetes
3. Designing an Operator: CRD, API, and Target Reconciliation
4. Developing an Operator with the Operator SDK
5. Developing an Operator: Advanced Functionality
6. Building and Deploying Your Kubernetes Operator
7. Packaging Operators for OperatorHub and Operator Lifecycle Manager
8. Preparing for Ongoing Maintenance of Your Operator
9. Diving into FAQs and Future Trends
10. Case Study for Optional Operator: Prometheus Operator
11. Case Study for Core Operator: Etcd Operator

✦ Table of Contents

Cover
Title Page
Copyright and Credits
Dedication
Contributors
Table of Contents
Preface
Part 1: Essentials of Operators and the Operator Framework
Chapter 1: Introducing the Operator Framework
Technical requirements
Managing clusters without Operators
Demonstrating on a sample application
Reacting to changing cluster states
Introducing the Operator Framework
Exploring Kubernetes controllers
Knowing key terms for Operators
Putting it all together
Developing with the Operator SDK
Managing Operators with OLM
Distributing Operators on OperatorHub.io
Defining Operator functions with the Capability Model
Using Operators to manage applications
Summarizing the Operator Framework
Applying Operator capabilities
Summary
Chapter 2: Understanding How Operators Interact with Kubernetes
Interacting with Kubernetes cluster resources
Pods, ReplicaSets, and Deployments
Custom resource definitions
ServiceAccounts, roles, and RoleBindings (RBAC)
Namespaces
Identifying users and maintainers
Cluster administrators
Cluster users
End users and customers
Maintainers
Designing beneficial features for your operator
Planning for changes in your Operator
Starting small
Iterating effectively
Deprecating gracefully
Summary
Part 2: Designing and Developing an Operator
Chapter 3: Designing an Operator – CRD, API, and Target Reconciliation
Describing the problem
Designing an API and a CRD
Following the Kubernetes API design conventions
Understanding a CRD schema
Example Operator CRD
Working with other required resources
Designing a target reconciliation loop
Level- versus edge-based event triggering
Designing reconcile logic
Handling upgrades and downgrades
Using failure reporting
Reporting errors with logging
Reporting errors with status updates
Reporting errors with events
Summary
Chapter 4: Developing an Operator with the Operator SDK
Technical requirements
Setting up your project
Defining an API
Adding resource manifests
Additional manifests and BinData
Writing a control loop
Troubleshooting
General Kubernetes resources
Operator SDK resources
Kubebuilder resources
Summary
Chapter 5: Developing an Operator – Advanced Functionality
Technical requirements
Understanding the need for advanced functionality
Reporting status conditions
Operator CRD conditions
Using the OLM OperatorCondition
Implementing metrics reporting
Adding a custom service metric
RED metrics
Implementing leader election
Adding health checks
Summary
Chapter 6: Building and Deploying Your Operator
Technical requirements
Building a container image
Building the Operator locally
Building the Operator image with Docker
Deploying in a test cluster
Pushing and testing changes
Installing and configuring kube-prometheus
Redeploying the Operator with metrics
Key takeaways
Troubleshooting
Makefile issues
kind
Docker
Metrics
Additional errors
Summary
Part 3: Deploying and Distributing Operators for Public Use
Chapter 7: Installing and Running Operators with the Operator Lifecycle Manager
Technical requirements
Understanding the OLM
Installing the OLM in a Kubernetes cluster
Interacting with the OLM
Running your Operator
Generating an Operator's bundle
Exploring the bundle files
Building a bundle image
Pushing a bundle image
Deploying an Operator bundle with the OLM
Working with OperatorHub
Installing Operators from OperatorHub
Submitting your own Operator to OperatorHub
Troubleshooting
OLM support
OperatorHub support
Summary
Chapter 8: Preparing for Ongoing Maintenance of Your Operator
Technical requirements
Releasing new versions of your Operator
Adding an API version to your Operator
Updating the Operator CSV version
Releasing a new version on OperatorHub
Planning for deprecation and backward compatibility
Revisiting Operator design
Starting small
Iterating effectively
Deprecating gracefully
Complying with Kubernetes standards for changes
Removing APIs
API conversion
API lifetime
Aligning with the Kubernetes release timeline
Overview of a Kubernetes release
Start of release
Enhancements Freeze
Call for Exceptions
Code Freeze
Test Freeze
GA release/Code Thaw
Retrospective
Working with the Kubernetes community
Summary
Chapter 9: Diving into FAQs and Future Trends
FAQs about the Operator Framework
What is an Operator?
What benefit do Operators provide to a Kubernetes cluster?
How are Operators different from other Kubernetes controllers?
What is the Operator Framework?
What is an Operand?
What are the main components of the Operator Framework?
What programming languages can Operators be written in?
What is the Operator Capability Model?
FAQs about Operator design, CRDs, and APIs
How does an Operator interact with Kubernetes?
What cluster resources does an Operator act on?
What is a CRD?
How is a CRD different from a CR object?
What Kubernetes namespaces do Operators run within?
How do users interact with an Operator?
How can you plan for changes early in an Operator's lifecycle?
How does an Operator's API relate to its CRD?
What are the conventions for an Operator API?
What is a structural CRD schema?
What is OpenAPI v3 validation?
What is Kubebuilder?
What is a reconciliation loop?
What is the main function of an Operator's reconciliation loop?
What are the two kinds of event triggering?
What is a ClusterServiceVersion (CSV)?
How can Operators handle upgrades and downgrades?
How can Operators report failures?
What are status conditions?
What are Kubernetes events?
FAQs about the Operator SDK and coding controller logic
What is the Operator SDK?
How can operator-sdk scaffold a boilerplate Operator project?
What does a boilerplate Operator project contain?
How can you create an API with operator-sdk?
What does a basic Operator API created with operator-sdk look like?
What other code is generated by operator-sdk?
What do Kubebuilder markers do?
How does the Operator SDK generate Operator resource manifests?
How else can you customize generated Operator manifests?
What are go-bindata and go:embed?
What is the basic structure of a control/reconciliation loop?
How does a control loop function access Operator config settings?
What information does a status condition report?
What are the two basic kinds of metrics?
How can metrics be collected?
What are RED metrics?
What is leader election?
What are the two main strategies for leader election?
What are health and ready checks?
FAQs about OperatorHub and the OLM
What are the different ways to compile an Operator?
How does a basic Operator SDK project build a container image?
How can an Operator be deployed in a Kubernetes cluster?
What is the OLM?
What benefit does running an Operator with the OLM provide?
How do you install the OLM in a cluster?
What does the operator-sdk olm status command show?
What is an Operator bundle?
How do you generate a bundle?
What is a bundle image?
How do you build a bundle image?
How do you deploy a bundle with the OLM?
What is OperatorHub?
How do you install an Operator from OperatorHub?
How do you submit an Operator to OperatorHub?
Future trends in the Operator Framework
How do you release a new version of an Operator?
When is it appropriate to add a new API version?
How do you add a new API version?
What is an API conversion?
How do you convert between two versions of an API?
What is a conversion webhook?
How do you add a conversion webhook to an Operator?
What is kube-storage-version-migrator?
How do you update an Operator's CSV?
What are upgrade channels?
How do you publish a new version on OperatorHub?
What is the Kubernetes deprecation policy?
How can API elements be removed in the Kubernetes deprecation policy?
How long are API versions generally supported?
How long is the Kubernetes release cycle?
What is Enhancements Freeze?
What is Code Freeze?
What is Retrospective?
How do Kubernetes community standards apply to Operator development?
Summary
Chapter 10: Case Study for Optional Operators – the Prometheus Operator
A real-world use case
Prometheus overview
Installing and running Prometheus
Configuring Prometheus
Summarizing the problems with manual Prometheus
Operator design
CRDs and APIs
Reconciliation logic
Operator distribution and development
Updates and maintenance
Summary
Chapter 11: Case Study for Core Operator – Etcd Operator
Core Operators – extending the Kubernetes platform
RBAC Manager
The Kube Scheduler Operator
The etcd Operator
etcd Operator design
CRDs
Reconciliation logic
Failure recovery
Stability and safety
Upgrading Kubernetes
Summary
Index
About Packt
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